WEBVTT MIKE TESELLE, KCRA 3 NEWS.rtTEO: THANK YOU.TONI: LET'S BRING IN OUR SCIENCEEXPERT, DIRK VERDOORN, FOR ALOOK AT SOME FACTORS IN ROCKSLIDES.WHAT CAUSES THIS?rtDIRK: WE HAVE THE HEATING OF THEDAY, THE COOLING OF THE NIGHT,ENDING YOU ADD WATER AND CAN GETBIGrt SLABS THAT COME OFF THEROCK.THIS IS WHERE THE LATESTROCKSLIDE HAPPEN.YOU CAN SEE THErt SECTION IN THEDISTANCE THAT IT HAD TO FALL.WE ARE GOING FROM 5800 FEET DOWNTO 4800 FEET WHERE ITrt HITS ANDTHEN IT SLIDES TO THE VALLEYFLOOR.THIS IS A BIG PIECE OF ROCK THATFELL OFF.BETWEEN 400 TO 500 FEET INLENGTH.rtTHAT IS MUCH BIGGER THAN THE ONEON WEDNESDAY.YOU HAVE THIS AREA EXPOSED TOTHrtE AIR.THAT IS THE LIGHTER ROCK.THE DARKER ROCKS ARE BECAUSE OFTHErt WATER.THE FREEZING TEMPERATURES ATNIGHT TURNS THE WATER TO ICE.AS THE WATER FREEZES, ITEXPANDS.rtTHAT HELPS TO CREATE MORE CRACKSAND MAKE IT MORE IN STABLE.I THINK THAT IS THE NATURALPROCESS GOING ON.YOU HAVErt THE ROCK WITH TOO MUCHWEIGHT TO BE HELD UP BY THE AREASUPPORTING IT.IT FALLS DOWN.

Two large rockfalls at El Capitan in Yosemite National Park left a man dead and two other people hurt, but this natural phenomenon is not all that uncommon.Rockfalls are a regular occurrence at Yosemite National Park, but more of them are not reported and they very rarely injure or kill people.The reason for rockfalls can be attributed to the heating of the day and the cooling of the night, paired with water, KCRA meteorologist Dirk Verdoorn said.The huge rock chunk that fell Thursday, injuring one person and sending a cloud of dust over Yosemite Valley, was between 400 and 500 feet in length.++Couple from Great Britain were victims of deadly Yosemite rockfallThe region has seen a very wet winter, so there is a lot of water still flowing through many parts of Yosemite.Oftentimes, the freezing temperatures at night causes the water on the rock formations to also freeze, and as water freezes, it expands. That creates more cracks and causes the rock to become more unstable, Verdoorn said.The heavy piece of rock that is cracked is eventually too much to be held up by the area that is supporting it, causing a chunk to come sliding off.It is a natural process and something that happens often, Verdoorn said.

SACRAMENTO, Calif. (KCRA) —

Two large rockfalls at El Capitan in Yosemite National Park left a man dead and two other people hurt, but this natural phenomenon is not all that uncommon.

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Rockfalls are a regular occurrence at Yosemite National Park, but more of them are not reported and they very rarely injure or kill people.

The reason for rockfalls can be attributed to the heating of the day and the cooling of the night, paired with water, KCRA meteorologist Dirk Verdoorn said.

The region has seen a very wet winter, so there is a lot of water still flowing through many parts of Yosemite.

Oftentimes, the freezing temperatures at night causes the water on the rock formations to also freeze, and as water freezes, it expands. That creates more cracks and causes the rock to become more unstable, Verdoorn said.

The heavy piece of rock that is cracked is eventually too much to be held up by the area that is supporting it, causing a chunk to come sliding off.

It is a natural process and something that happens often, Verdoorn said.